1. Field of the Invention
The present invention relates to a method and apparatus for magnetic transfer, for transferring a desired magnetic pattern from a magnetic transfer master carrier to a transfer medium. The present invention also relates to a magnetic recording medium.
2. Description of the Related Art
Conventionally, magnetic transfer methods that transfer magnetic patterns corresponding to information from a master carrier to a transfer medium (slave medium) are known. Magnetic transfer is performed by placing the master carrier bearing the magnetic pattern in close contact with the slave medium, which has a magnetic recording layer. Then, a transfer magnetic field is applied to the master carrier and the slave medium while they are in a state of close contact, to transfer and record the magnetic pattern onto the slave medium. Magnetic transfer is advantageous in that it enables static recording of information without changing the relative positions of the master carrier and the slave medium, and also capable of recording in an extremely short period of time (refer to Japanese Unexamined Patent Publication Nos. 10(1998)-040544 and 10(1998)-269566).
It has already been proposed in Japanese Unexamined Patent Publication Nos. 10(1998)-040544 and 10(1998)-269566 to record servo signals, for positioning heads, onto magnetic recording media by magnetic transfer.
Meanwhile, there is a technical problem associated with magnetic transfer. That is, during transfer of signals from the master carrier to the slave medium, unclear (inversely magnetized) magnetic recording portions are generated. Sub-pulses are detected within readout waveforms of the magnetic pattern due to the presence of these unclear magnetic recording portions. The sub-pulses may be recognized as reproduction signals by a magnetic reproduction apparatus, causing errors in readout. Methods for observing the sub-pulses, which are generated due to the presence of the unclear magnetic recording portions, are disclosed in U.S. patent application Publication No. 20020044368 and Japanese Unexamined Patent Publication No 2002-042301.
The present inventors have performed research, and found that sub-pulses do not occur at portions of the uneven magnetic pattern, which is provided on the master carrier, at which protrusions are densely formed. On the other hand, sub-pulses occurred with high frequency at portions of the pattern at which protrusions are sparsely formed.